Automotive HVAC Diffuser With Cooperating Wall Guide And Vane

ABSTRACT

A case for an HVAC system has at least two molded shells joined together along a parting line to enclose a heat exchanger chamber, a blower chamber, and a diffuser section. The diffuser section includes a floor, a ceiling, an outer wall, and an inner wall around a longitudinal axis. The walls provide an airflow path through the diffuser between the blower and heat exchanger chamber, and the airflow path makes a substantially right angle turn into the heat exchanger chamber which results in a tendency to create a high flow region at the outer wall because of centrifugal effects. The outer wall is shaped to form a wall guide partially projecting into the airflow path in the diffuser, wherein the wall guide has an upstream encroaching surface and a downstream retreating surface so that a portion of the guided air is directed from the outer wall toward the inner wall. At least one of the floor or the ceiling includes a vane projecting into and deflecting the guided air in the airflow path, wherein the vane has an upstream end proximate to the wall guide and a downstream end extending toward the heat exchanger chamber for initiating a portion of the substantially right angle turn for a portion of the airflow.

CROSS REFERENCE TO RELATED APPLICATIONS

Not Applicable.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH

Not Applicable.

BACKGROUND OF THE INVENTION

The present invention relates in general to a case for an automotiveHVAC system, and, more specifically, to wall guide and vane features forimproving air flow into an evaporator core.

In a typical automotive HVAC system, a blower delivers fresh orrecirculated air to heat exchangers (e.g., an evaporator) which is thendistributed to the passenger cabin via ducts. A diffuser couples the airstream from the blower to the evaporator. Due to space requirements, thediffuser turns the air stream by about 90° for delivery to theevaporator. Conventional blower/diffuser combinations produce anon-uniform flow that tends to produce high flows on the outer peripheryof the diffuser due to centrifugal forces, and the high flow becomesconcentrated at one end of the evaporator.

A uniform velocity distribution at the diffuser outlet and into theevaporator is very desirable to ensure efficient evaporator performance,higher total air flow, and reduced noise generation as the air passesthrough the evaporator core. Prior attempts to improve the uniformity ofthe air flow have included the addition of aerodynamic vanes in theinterior or at the walls of the diffuser.

The diffuser is normally made as a molded plastic part. The height ofinterior vanes from a corresponding wall have been restricted due tolimitations in the molding process and limitations associated withhandling of the part after molding (e.g., breakage of the vanes).Therefore, vanes can affect the air flow near to the diffuser walls butare less able to affect air flow near the midline of the diffuser.Furthermore, the die draw of the molding process does not allow vanes toextend from walls that are perpendicular to one another (i.e., vanescannot extend from both the curved outer peripheral wall and either ofthe transverse (i.e., floor and ceiling) walls in the same moldedsection).

For similar reasons, structures built directly into the side walls havea greater influence on air flow in the regions of those walls. Prior artsystems have, nevertheless, achieved some improvements in flowuniformity using vanes and wall structures to diffuse the air stream.However, it would be desirable to reduce the complexity and to increasethe efficiency of such structures.

SUMMARY OF THE INVENTION

The present invention overcomes limitations of the prior art bycombining effects of a wall guide and a vane together to achieve uniformairflow across the evaporator core.

In one aspect of the invention, a case for an HVAC system in atransportation vehicle comprises at least two molded shells joinedtogether along a parting line to receive a heat exchanger and a blower.The shells enclose a heat exchanger chamber, a blower chamber, and adiffuser section for guiding air from the blower chamber to the heatexchanger chamber. The diffuser section includes a floor, a ceiling, anouter wall, and an inner wall around a longitudinal axis between aninlet and an outlet. The walls provide an airflow path through thediffuser between the blower and heat exchanger chamber, and the airflowpath makes a substantially right angle turn into the heat exchangerchamber which results in a tendency to create a high flow region at theouter wall because of centrifugal effects. The outer wall is shaped toform a wall guide partially projecting into the airflow path in thediffuser, wherein the wall guide has an upstream encroaching surface anda downstream retreating surface so that a portion of the guided air isdirected from the outer wall toward the inner wall. At least one of thefloor or the ceiling includes a vane projecting into and deflecting theguided air in the airflow path, wherein the vane has an upstream endproximate to the wall guide and a downstream end extending toward theheat exchanger chamber for initiating a portion of the substantiallyright angle turn for a portion of the airflow.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram showing blower, diffuser, and evaporatorsections of an HVAC case for a first embodiment of the invention.

FIG. 2 is a schematic diagram showing a wall guide in greater detail.

FIG. 3 is a close-up perspective view of a wall guide according to oneembodiment.

FIG. 4 is a close-up perspective view of a wall guide according toanother embodiment.

FIG. 5 is a plan view showing a preferred relationship between a wallguide and vane in greater detail.

FIG. 6 is an interior perspective view of an alternative embodimentshowing blower and diffuser sections of an HVAC case.

FIG. 7 is an interior perspective view of another alternative embodimentincluding cooling fins of a variable blower control.

FIG. 8 illustrates an alternative vane shape.

FIG. 9 is a schematic diagram showing blower, diffuser, and evaporatorsections of an HVAC case having an alternative relationship between thevane and wall guide.

FIG. 10 is a perspective view of an embodiment wherein vanes provideairflow shaping near floor and ceiling areas and a wall guide providesairflow shaping in a parting-line area.

FIG. 11 is a top view of the lower shell portion along line 11-11 ofFIG. 10 coinciding with the parting line.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Referring now to FIG. 1, an HVAC case 10 includes a blower section 11,an evaporator section 12, and an intervening diffuser section 13. Blowersection 11 receives a motor-driven bladed wheel (not shown) for createdan air flow of fresh or recirculated air that is guided through diffusersection 13 to an evaporator core (not shown) mounted in evaporatorsection 12. Guided air 14 follows an airflow path and is required tomake an approximately right angle turn in order to enter evaporator issection 12.

Diffuser section 13 includes an outer wall 15, an inner wall 16, a floor17, and a ceiling (not shown) that surround a generally longitudinalaxis of diffuser section 13 that extends between an inlet from theblower section 11 and an outlet to evaporator section 12. Due tocentrifugal affects, a region of high flow is generally associated withouter wall 15 which results in non-uniform entry of the air flow intoevaporator section 12. To improve uniformity and to reduce the generallyhigh flow along outer wall 15, the present invention employs a wallguide 20 and a vane 21 for interacting with the guided air 14 andredirecting it in a beneficial manner.

Wall guide 20 is shown in greater detail in FIG. 2. Wall guide 20 has anencroaching surface 25 on its upstream side and a retreating surface 26on its downstream side. A transition 27 lies between surfaces 25 and 26.Wall guide 20 functions to turn some of the air away from a region 30(that would otherwise have a high flow) into a region 31 of typicallylesser flow, thereby reducing or eliminating local regions of lower orhigher velocity in the flow, and thus increasing evaporator coverage.

One embodiment of a wall guide 35 is shown in greater detail in FIG. 3.Outer wall 15 is part of an injection molded case component or shell,typically formed of a thermal plastic. Wall guide 35 is formed as adepression into the molded shell and has an upstream encroaching surface36 and a downstream retreating surface 37. Preferably, upstream surface36 has a generally concave shape for efficient deflection of airflow andlow noise generation. Surface 36 may be comprised a curved plane (i.e.,wherein a longitudinal cross-section reveals the concave shape). Edges38 and 39 may be rounded to avoid turbulence. A radius of curvature forthe concave upstream surface 36 is preferably in the range of about 15to about 100 mm.

The shape of downstream surface 37 is less critical. As shown in FIG. 3,a generally flat or slightly convex shape is acceptable. Such shapes mayhave manufacturing advantages. More preferably, however, a concave shapemay be employed as shown in FIG. 4. Thus, a wall guide 40 has a concaveupstream surface 41 and a concave downstream surface 42, with atransition 43 having a generally convex shape. The generally concaveshape of downstream surface 42 preferably has a radius of curvaturegreater than about 100 mm. The generally convex shape of transition 43preferably has a radius of curvature less than about 40 mm. Thecurvatures of the surfaces can alternatively vary continuously over thelength of the wall guide, with the three sections merging smoothly intoone another. The contours can be optimized to delay the point ofseparation of flow (e.g., using design techniques known for constructingCoanda airfoils).

Use of a wall guide together with a vane is shown in FIG. 5. A wallguide 45 formed in outer wall 15 has an upstream surface 46 anddownstream surface 47. A vane 50 projects upward from floor 17 and hasan upstream end 51 proximate to wall guide 45 and a downstream end 52that extends down the airflow path and toward the evaporator chamberhaving a curvature that initiates a portion of the substantially rightangle turn to be made for a portion of the air flow that flows to theinitial portion of the evaporator chamber. Upstream end 51 extends in adirection substantially parallel to the longitudinal axis of thediffuser and preferably has its tip proximate to and directly opposed toa transition 48 of wall guide 45. Because downstream surface 47 isretreating, a cross-sectional area between vane 50 and wall guide 45steadily increases in the airflow direction due to an increasing widthfrom a first gap 55 to a second gap 56. Due to the increasingcross-sectional area, the guided air that passes through a region 57 hasa reduction in its speed resulting from the Bernoulli Effect. By slowingdown the airflow in this region, the beneficial effect of wall guide 45is enhanced and the tendency of a concentrated flow along outer wall 15is counteracted. Moreover, the curvature of downstream end 52 furtherdistributes airflow toward the initial side of the evaporator chambernormally receiving a lower flow. Thus, a high degree of uniformity ofairflow can be achieved.

FIG. 6 shows yet another embodiment of an HVAC case 60 including ablower section 61 and a diffuser section 62. Case 60 is comprised of amolded shell having a upper shell 63 and a lower shell 64. An outer wallof diffuser section 62 includes a wall guide 65 in upper shell 63 and awall guide 66 in lower shell 64. A guide vane 67 extends from floor 68and interacts with wall guides 65 and 66 as previously described. Ifdesired, another vane can be formed extending from ceiling 69 ofdiffuser section 62. Any combination of wall guides and vanes could beused. The beneficial effects of the invention can still be achieved evenif there is only one wall guide and one vane and they are formed in theopposite shells.

FIG. 7 shows an example with a lower shell 70 having a wall guide 71 andan upper shell 72 having a vane 73. Cooling fins 74 of a variable blowercontrol (VBC) electronic module mounted to the outside of the case canalso enter the airflow path to further direct the guided air in adesired direction.

The cross-sectional shape of the vane may be streamlined as shown inFIG. 8. Thus, a vane 80 has an extended teardrop shape with a roundedupstream end (leading edge) 81 and a tapered downstream end (trailingedge) 82. The teardrop shape can be designed using Coanda airfoil designtechniques. It is effective at avoiding undesirable recirculations orturbulence of air as it separates from vane 80.

FIG. 9 illustrates an alternative relationship between a wall guide anda vane wherein a wall guide 85 and vane 86 track one another in aside-by-side relationship to define a curved air channel 87. Air flowingthrough channel 87 is deflected along a curving trajectory toward theentrance to evaporator section 12. The curved channel keeps the airflowattached to the vane for longer, and is more effective at bending ittoward evaporator section 12.

FIG. 10 is an end, perspective view looking generally along an airflowpath and illustrating another alternative relationship between a wallguide and vanes. An upper shell 90 and a lower shell 91 meet along aparting line 96. Upper shell 90 has a vane 92 extending from itsceiling, and lower shell 91 has a vane 93 extending from its floor. Theshells also form a wall guide 94, 95 in an outer wall such that wallguide 94, 95 spans the region around parting line 96. Wall guide 94, 95modifies the airflow path in the parting-line region (between the floorand ceiling, and therefore between vanes 92 and 93) where the vanescannot operate due to limitations in height that can be created withinjection molding.

Vane 93 extends to a height 97 above the floor. Parting line 96 is at aheight 98 above the floor. The height of a vane may typically be limitedto about 50 to about 75 millimeters. This may comprise about 60% to 70%of the distance of the floor or ceiling to the parting line. As aresult, about 30% to 40% or more of the height of the airflow betweenfloor and ceiling cannot be effectively shaped by the vanes. Thus, FIG.10 uses a wall guide to provide at least a partially modified airflow inthe parting-line region. Wall guide 94, 95 may also extend oversubstantially the entire floor to ceiling distance as shown in FIGS. 10and 11.

1. A case for an HVAC system in a transportation vehicle, comprising atleast two molded shells joined together along a parting line to receivea heat exchanger and a blower, wherein the shells enclose a heatexchanger chamber, a blower chamber, and a diffuser section for guidingair from the blower chamber to the heat exchanger chamber; wherein thediffuser section includes a floor, a ceiling, an outer wall, and aninner wall around a longitudinal axis between an inlet and an outlet;wherein the walls provide an airflow path through the diffuser betweenthe blower and heat exchanger chamber, and wherein the airflow pathmakes a substantially right angle turn before entering the heatexchanger chamber which results in a tendency to create a high flowregion at the outer wall because of centrifugal effects; wherein theouter wall is shaped to form a wall guide partially projecting into theairflow path in the diffuser, wherein the wall guide has an upstreamencroaching surface and a downstream retreating surface so that aportion of the guided air is directed from the outer wall toward theinner wall; and wherein at least one of the floor or the ceilingincludes a vane projecting into and deflecting the guided air in theairflow path, wherein the vane and wall guide cooperate to mutuallydirect the guided air from the outer wall toward the inner wall.
 2. Thecase of claim 1 wherein the vane extends to a first height which is lessthan about 70 percent of a height of the parting line, and wherein thewall guide spans a region around the parting line.
 3. The case of claim1 wherein the vane has an upstream end proximate to the wall guide and adownstream end extending toward the heat exchanger chamber forinitiating a portion of the substantially right angle turn for a portionof the airflow.
 4. The case of claim 1 wherein at least a portion of theupstream end of the vane extends substantially parallel to the localflow so that a region of the airflow path between the vane and thedownstream returning surface has an increasing cross-sectional area thatcauses guided air passing through the region to have a reduction inspeed by the Bernoulli Effect.
 5. The case of claim 1 wherein thedownstream end of the vane has an extended teardrop shape.
 6. The caseof claim 1 wherein the upstream encroaching surface of the wall guideincludes a generally concave shape with a radius of curvature in therange of about 15 to about 100 millimeters.
 7. The case of claim 1wherein the downstream retreating surface of the wall guide includes agenerally concave shape with a radius of curvature greater than about100 millimeters.
 8. The case of claim 1 wherein the wall guide furtherincludes a transition between the upstream encroaching surface and thedownstream retreating surface having a generally convex shape with aradius of curvature less than about 40 millimeters.
 9. The case of claim1 wherein the cooperation of the wall guide and vane is comprised of thewall guide and vane being disposed in a side-by-side relationship todefine a curved air channel, whereby the guided air is deflected along acurving trajectory toward the heat exchanger chamber.